Java 在JComboBox中使用向上/向下箭头滚动时，它不应该'；t更新显示所选项目的顶部互动程序

我希望我的combobox顶部互动程序仅在按enter键时更新，而不是在使用上/下箭头滚动时更新

当前，当我使用向上/向下箭头滚动时，当前突出显示的当前项目将在

JComboBox

的顶部磁贴中更新为选中项目。我需要避免这种情况

这是我的密码。提前谢谢

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class SwingControlDemo {
    private JFrame mainFrame;
    private JLabel headerLabel;
    private JLabel statusLabel;
    private JPanel controlPanel;

    public SwingControlDemo() {
        prepareGUI();
    }

    public static void main(String[] args) {
        SwingControlDemo swingControlDemo = new SwingControlDemo();
        swingControlDemo.showComboboxDemo();
    }

    private void prepareGUI() {
        mainFrame = new JFrame("Java Swing Examples");
        mainFrame.setSize(400, 400);
        mainFrame.setLayout(new GridLayout(3, 1));
        mainFrame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent windowEvent) {
                System.exit(0);
            }
        });
        headerLabel = new JLabel("", JLabel.CENTER);
        statusLabel = new JLabel("", JLabel.CENTER);

        statusLabel.setSize(350, 100);

        controlPanel = new JPanel();
        controlPanel.setLayout(new FlowLayout());

        mainFrame.add(headerLabel);
        mainFrame.add(controlPanel);
        mainFrame.add(statusLabel);
        mainFrame.setVisible(true);
    }

    private void showComboboxDemo() {
        headerLabel.setText("Control in action: JComboBox");

        final DefaultComboBoxModel fruitsName = new DefaultComboBoxModel();

        fruitsName.addElement("Apple");
        fruitsName.addElement("Grapes");
        fruitsName.addElement("Mango");
        fruitsName.addElement("Peer");
        fruitsName.addElement("java");
        fruitsName.addElement("Mango");

        final JComboBox fruitCombo = new JComboBox(fruitsName);
        fruitCombo.setSelectedIndex(0);

        JScrollPane fruitListScrollPane = new JScrollPane(fruitCombo);

        JButton showButton = new JButton("Show");

        fruitCombo.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent arg0) {
                if (arg0.getModifiers() == ActionEvent.MOUSE_EVENT_MASK || arg0.getModifiers() == ActionEvent.KEY_EVENT_MASK || true) {
                    System.out.println("arg0" + "  " + arg0.getModifiers());
                }
            }
        });

        fruitCombo.addKeyListener(new KeyListener() {
            @Override
            public void keyTyped(KeyEvent arg0) {
                // TODO Auto-generated method stub
            }

            @Override
            public void keyReleased(KeyEvent arg0) {
                // TODO Auto-generated method stub
                if (arg0.getKeyCode() == KeyEvent.VK_ENTER) {
                    System.out.println("enter key pressed" + arg0.getKeyCode());
                }
            }

            @Override
            public void keyPressed(KeyEvent arg0) {
                // TODO Auto-generated method stub
            }
        });

        System.out.println(fruitCombo.getComponentListeners().toString());
        controlPanel.add(fruitListScrollPane);
        controlPanel.add(showButton);
        mainFrame.setVisible(true);
    }
}

---

您可以在组合框上设置一个属性，以防止在使用箭头键时触发事件：

comboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);

注意：使用上述属性时，您可能需要（也可能不需要）手动关闭弹出窗口：

/*
    This works on non editable combo boxes
*/
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.*;
import javax.swing.text.*;

public class ComboBoxAction extends JFrame implements ActionListener
{
    public ComboBoxAction()
    {
        JComboBox<String> comboBox = new JComboBox<String>();
        comboBox.addActionListener( this );

        comboBox.addItem( "Item 1" );
        comboBox.addItem( "Item 2" );
        comboBox.addItem( "Item 3" );
        comboBox.addItem( "Item 4" );

        //  This prevents action events from being fired when the
        //  up/down arrow keys are used on the dropdown menu

        comboBox.putClientProperty("JComboBox.isTableCellEditor", Boolean.TRUE);

        getContentPane().add( comboBox );
        getContentPane().add( new JTextField(), BorderLayout.SOUTH );
    }

    public void actionPerformed(ActionEvent e)
    {
        System.out.println( e.getModifiers() );

        JComboBox comboBox = (JComboBox)e.getSource();
        System.out.println( comboBox.getSelectedItem() );

        //  make sure popup is closed when 'isTableCellEditor' is used

//      comboBox.hidePopup();
    }

    public static void main(String[] args)
    {
        ComboBoxAction frame = new ComboBoxAction();
        frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
        frame.pack();
        frame.setVisible( true );
     }
}

/*
这适用于不可编辑的组合框
*/
导入java.awt.*；
导入java.awt.event.*；
导入javax.swing.*；
导入javax.swing.plaf.basic.*；
导入javax.swing.text.*；
公共类ComboBoxAction扩展JFrame实现ActionListener
{
公共行动（）
{
JComboBox comboBox=新的JComboBox（）；
comboBox.addActionListener（这个）；
组合框。附加项（“第1项”）；
组合框。附加项（“第2项”）；
组合框。附加项（“第3项”）；
组合框。附加项（“第4项”）；
//这样可以防止在
//上/下箭头键用于下拉菜单
comboBox.putClientProperty（“JComboBox.isTableCellEditor”，Boolean.TRUE）；
getContentPane（）.add（组合框）；
getContentPane（）.add（新的JTextField（），BorderLayout.SOUTH）；
}
已执行的公共无效操作（操作事件e）
{
System.out.println（e.getModifiers（））；
JComboBox组合框=（JComboBox）e.getSource（）；
System.out.println（comboBox.getSelectedItem（））；
//确保在使用“isTableCellEditor”时关闭弹出窗口
//comboBox.hidePopup（）；
}
公共静态void main（字符串[]args）
{
ComboBoxAction帧=新ComboBoxAction（）；
frame.setDefaultCloseOperation（关闭时退出）；
frame.pack（）；
frame.setVisible（true）；
}
}

我找到了一个使用自定义键绑定操作的解决方案。下面是包含这些更改的代码

package abcd;

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.plaf.basic.BasicComboPopup;

public class SwingControlDemo {

   private JFrame mainFrame;
   private JLabel headerLabel;
   private JLabel statusLabel;
   private JPanel controlPanel;

   public SwingControlDemo(){
      prepareGUI();
   }

   public static void main(String[] args){
      SwingControlDemo  swingControlDemo = new SwingControlDemo();      
      swingControlDemo.showComboboxDemo();
   }

   private void prepareGUI(){
      mainFrame = new JFrame("Java Swing Examples");
      mainFrame.setSize(400,400);
      mainFrame.setLayout(new GridLayout(3, 1));
      mainFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent windowEvent){
            System.exit(0);
         }        
      });    
      headerLabel = new JLabel("", JLabel.CENTER);        
      statusLabel = new JLabel("",JLabel.CENTER);    

      statusLabel.setSize(350,100);

      controlPanel = new JPanel();
      controlPanel.setLayout(new FlowLayout());

      mainFrame.add(headerLabel);
      mainFrame.add(controlPanel);
      mainFrame.add(statusLabel);
      mainFrame.setVisible(true);  
   }

   private void showComboboxDemo(){                                    
      headerLabel.setText("Control in action: JComboBox"); 

      final DefaultComboBoxModel fruitsName = new DefaultComboBoxModel();

      fruitsName.addElement("Apple");
      fruitsName.addElement("Grapes");
      fruitsName.addElement("Mango");
      fruitsName.addElement("Peer");
      fruitsName.addElement("java");
      fruitsName.addElement("mkm");

      final JComboBox fruitCombo = new JComboBox(fruitsName);
      fruitCombo.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT).put(KeyStroke.getKeyStroke("DOWN"), "cDownArrow");
      fruitCombo.getInputMap(JComponent.WHEN_ANCESTOR_OF_FOCUSED_COMPONENT).put(KeyStroke.getKeyStroke("UP"), "cUpArrow");
      Action customDownArrow = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            // TODO Auto-generated method stub
            System.out.println("in");
            JComboBox box = (JComboBox)arg0.getSource();
            BasicComboPopup pop = (BasicComboPopup)box.getAccessibleContext().getAccessibleChild(0);
            JList list  = pop.getList();
            System.out.println("next index" + "  "+ (list.getSelectedIndex()+1)%box.getItemCount());
            list.setSelectedIndex((list.getSelectedIndex()+1)%box.getItemCount());

        }
    };

    Action customUpArrow = new AbstractAction() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            // TODO Auto-generated method stub
            JComboBox box = (JComboBox)arg0.getSource();
            BasicComboPopup pop = (BasicComboPopup)box.getAccessibleContext().getAccessibleChild(0);
            JList list  = pop.getList();
            System.out.println("next index" + "  "+ (list.getSelectedIndex()+1)%box.getItemCount());
            list.setSelectedIndex(((list.getSelectedIndex()-1)%box.getItemCount()+box.getItemCount())%box.getItemCount());
        }
    };
      fruitCombo.getActionMap().put("cDownArrow",customDownArrow);
      fruitCombo.getActionMap().put("cUpArrow", customUpArrow);
      fruitCombo.setSelectedIndex(0);

      JScrollPane fruitListScrollPane = new JScrollPane(fruitCombo);    

      JButton showButton = new JButton("Show");



      fruitCombo.addActionListener(new ActionListener() {

        @Override
        public void actionPerformed(ActionEvent arg0) {
            if(arg0.getModifiers()==ActionEvent.MOUSE_EVENT_MASK || arg0.getModifiers()==ActionEvent.KEY_EVENT_MASK||true){
                System.out.println("arg0"+"  "+arg0.getModifiers());
            }


        }
    });

      /*fruitCombo.addKeyListener(new KeyListener() {

        @Override
        public void keyTyped(KeyEvent arg0) {
            // TODO Auto-generated method stub

        }

        @Override
        public void keyReleased(KeyEvent arg0) {
            // TODO Auto-generated method stub
            if(arg0.getKeyCode()==KeyEvent.VK_ENTER){
                System.out.println("enter key pressed"+arg0.getKeyCode());
            }

        }

        @Override
        public void keyPressed(KeyEvent arg0) {
            // TODO Auto-generated method stub

        }
    });*/
      System.out.println(fruitCombo.getComponentListeners().toString());
      controlPanel.add(fruitListScrollPane);          
      controlPanel.add(showButton);    
      mainFrame.setVisible(true);             
   }
}

---

Oracle java已经解决了这个问题，因为它与使用鼠标的选择不一致。 但要启用修复程序，我们必须使用键“ComboBox.noActionOnKeyNavigation”更改默认SWING UI属性。在源代码中实现的修复中，他们将此属性用作标志。若我们将其设为真，那个么使用键盘选择JComboBox将不会触发动作事件。 此链接将为您提供修复的详细信息。这是来自OpenJDK的，但我已经在OracleJDK1.8.111中确认了这一点

所以基本上我们必须增加这条车道

---

UIManager.getLookAndFeelDefaults（）.put（“ComboBox.noActionOnKeyNavigation”，true）

旁注：

mainFrame.setDefaultCloseOperation（WindowConstants.EXIT_ON_CLOSE）而不是
mainFrame.addWindowListener（..
。旁注2:
X | | true
对于任何布尔表达式
X
，总是计算为
true
。删除
在
水果组合中的
actionPerformed
实现中的
true
。添加ActionListener
是为了在执行操作时检查修饰符上的某些值ng鼠标..旁注3：仅在上构造和操作Swing GUI对象。这个答案不正确。我们正在列表元素中选择项。我相信JComboBox上的滚动条是根据JcombBox中的选择移动的，而不是根据列表中的选择移动的。因此，如果我们确实喜欢这个答案中提到的，滚动条不会根据yo移动你的选择。我不赞成使用这个解决方案。我尝试过这个，但它改变了JcomboBox按钮的外观。你有什么解决方案吗？